Light-emitting diodes (LEDs) are manufactured by forming active regions on a substrate and by depositing various conductive and semiconductive layers on the substrate. The radiative recombination of electron-hole pairs can be used for the generation of electromagnetic radiation (e.g., light) by the electric current in a p-n junction. In a forward-biased p-n junction fabricated from a direct band gap material, such as GaAs or GaN, the recombination of the electron-hole pairs injected into the depletion region causes the emission of electromagnetic radiation. The electromagnetic radiation may be in the visible range or may be in a non-visible range. Different colors of LEDs may be created by using materials with different band gaps. Further, an LED with electromagnetic radiation emitting in a non-visible range may direct the non-visible light towards a phosphor lens or a like material type. When the non-visible light is absorbed by the phosphor, the phosphor emits a visible light.
Generally, the LED structure is formed by epitaxially growing layers of group III-V compounds such that layers of oppositely doped layers of a group III-V material are placed on either side of a light-emitting layer. During the formation of the group III-V epitaxy layer, such as a GaN layer, a dielectric layer of SiNx may form, adversely affecting the performance of the LED structure. To prevent the formation of SiNx, a metal transition layer is frequently deposited over the substrate prior to forming the LED structure.
The use of a metal transition layer, however, may adversely affect the crystal structure of the epitaxial GaN layer. The high temperatures used during the epitaxial growth process may cause metal atoms of the transition layer to inter-mix with the silicon atoms of the substrate, thereby forming complex structures. The complex structures resulting from the inter-mixing of the metal atoms and the silicon atoms are generally poly-crystalline or amorphous, which do not provide a good crystalline structure upon which an epitaxial process may be used to form the LED structure.
Accordingly, there is a need for an LED device, and a method of manufacturing, such that the inter-mixing of the metal atoms and the silicon atoms is reduced or prevented.